Hunt, Rebecca. Mr. Chartwell

Winston Churchill fought a life-long battle with clinical depression. He characterized that depression as being a big black dog that bedeviled him. In "Mr. Chartwell," Rebecca Hunt takes that metaphorical description and makes it literal. Churchill's depression is literally a big black dog who gives his name variously as Mr. Chartwell (Chartwell being the name of Churchill's home estate) and Black Pat.

When widowed and lonely young librarian Esther Hammerhans advertises for a boarder, she is unprepared for who turns up to take the room. A huge, talking black dog who walks on his hind legs and cracks impenetrable jokes and whose name is Black Pat is not exactly whom she expected. But she finds herself unable to say no and he moves into her spare room, and, from there, into the rest of her life and her house. After an encounter with Churchill in which each recognizes the other as an unwilling companion of the obnoxious dog, Esther comes to realize that if she cannot find the willpower to deny Black Pat entry into her life, she will be trapped with him for the rest of her life...which might not be terribly long under his baleful influence.